1. Field of the Invention
This invention relates generally to warm air frost control systems. More particularly, this invention relates to a frost control system for discharging heated air at the bottom portion of a frost controlled surface and advantageously inhibits the formation of frost on upper portions of the frost controlled surface by means of convection forces.
2. Background of the Invention
Large scale cold-storage lockers have been devised in order to accommodate the large capacity storage needs of the food industry. These lockers must accommodate the access needs of the user. As such these lockers are constructed with openings which can be easily opened and closed as well as provide an adequate barrier between the cold air compartment of the locker and the outside environment.
In order to provide easy access to a cold-storage locker compartment, various door systems have been devised depending upon the space requirements and the preferences of the user. These doors can be folding doors which are drawn laterally in a manner similar to curtains in the home. Others slide vertically in a manner analogous to the opening and closing of typical sliding garage doors while still other doors are mounted upon a vertical axis and swing open and close in the same manner as a gate. These are of course only a few examples of the many types of freezer access doors known to those skilled in the art.
A common problem associated with the aforementioned freezer door systems, regardless of their method of opening and closing, is the tendency of moisture to condense on the warm air side of the moveable freezer door. The condensation may drip to the floor of the freezer entrance resulting in a hazardous surface for persons entering and leaving the cold-storage locker. Frequently, the condensation freezes upon the hinges and other surfaces of the freezer door as well as surfaces adjacent to the door such as the floor. The accumulated frost hampers the opening and closing of the entrance to the cold-storage locker. Frosted or iced transparent door panels or windows obstruct vision to the other side of the door creating a safety hazard for persons entering and leaving the storage locker. Freezing of the joints presents the danger of locking the joints of the door. Attempts to free the locked joints may damage the freezer door. Therefore, it is advantageous to include a frost control system to prevent the condensation of water vapor upon the outer surface of the door, keep the door frost-free, maintain clear visibility through transparent portions of the door, and avoid frost buildup on the floor and other surfaces adjacent to the door.
Known systems for preventing the condensation of frost on the outside surface of a cold-storage locker door or to defrost a frost covered door have utilized radiant heat. These systems suffer from the presence of unequal application of heat upon the defrost surface. Since the amount of radiant energy incident upon the door surface is proportional to the area covered by the dispersed radiant energy, the portions of the door nearest to the heat source tend to receive too much heat while portions of the door farther away tend to receive an insufficient amount of heat to keep the door frost free. As a result, these systems are not desirable for large doors where the amount of heat per unit surface area changes greatly as one moves from the point of the door surface nearest to the heat source to the point farthest from the heat source.
Other known systems operate by blowing warm air downward and against the outer, warm-air, surface of the freezer door from a position located above the freezer door. A powerful blower is required in order to blow the warm air to the bottom of the freezer door surface since convection forces tend to halt the downward flow of the warmed air. It has been noted that such systems do not function optimally unless a second door is added to create a closed environment proximate the storage locker door in which the warm air circulates.